In a heat pump system it is often desirable to heat the oil reservoir of a hermetic compressor to vaporize any refrigerant condensate accumulating in the reservoir. This becomes especially important when operating the system in the heating mode under cold ambient conditions, because cold ambient air condenses the refrigerant which dilutes the oil. Heating the oil in the reservoir vaporizes the refrigerant and consequently removes it from the oil reservoir.
Present attempts at maximizing heat transfer to the oil and refrigerant involve inserting a heater deeply into a fabricated heater well that extends to the center of the oil reservoir. The well is generally in the shape of a cylindrical tube closed at one end, and extending its closed end through the compressor shell and into the oil reservoir, requires machining a hole through the shell. The open end of the well must be carefully welded to the perimeter of the hole to obtain a hermetic seal.
Even though the heater is located generally near the center of the oil reservoir, this is not the most effective location for vaporizing condensed refrigerant. Typically, condensed refrigerant is heavier than oil and settles at the bottom of the reservoir. With the heater near the center of the reservoir, heat must raise the temperature of a relatively long heater well and transfer through the oil before heating the refrigerant.
The central location becomes an even greater problem when a PTC heater (heater having a positive temperature coefficient) is used during cold start-up conditions. The PTC heater's resistance, which increases with an increase in temperature, is relatively low when the heater is centrally located and surrounded by cold, heat conductive oil. The low resistance increases the heater's wattage (V.sup.2 /R). This wasteful increase in power consumption heats the oil and also the relatively long heater well before indirectly heating the condensed refrigerant.
Therefore, an object of this invention is to more directly heat the refrigerant condensate in the oil reservoir of a hermetic compressor.
Another object is to mount a conventional PTC heater so that it heats at a higher temperature yet consumes less wattage.
Another object is to mount an oil heater in a fixture that is relatively easy and inexpensive to manufacture.
Yet another object is to provide a seamless indentation that is stronger and less likely to leak than a conventional fabricated well.
Still another object is to provide a heater fixture that only requires adhesive tape to mount its associated heater in place.
These and other objects will be apparent from the attached drawings and the description of the preferred embodiments that follow below.